Communications within large buildings is generally done with twisted telephone wire. This type of system is generally adequate for telephone and FAX communications and for most computer communications including internet communications. However, for video and other image communication systems, higher bandwidth is needed. This higher bandwidth is generally provided using coaxial cables or optical fibers. Providing large buildings, such as a multi-story building, with coaxial cables or fiber optics can be very expensive, especially for old buildings. Techniques for providing free space optical communications are known. (See "A Brief History of Free-Space Laser Communications" by David L. Begley in Selected Papers on Free-Space Laser Communications, David L. Begley, ed., SPIE Optical Engineering Press, 1991.)
What is needed is an inexpensive, high bandwidth communication system for large buildings.